Although caregivers often become concerned about their child by 17-19 months of age, children do not typically receive a diagnosis of autism spectrum disorder (ASD) until they are 41/2 years old, or older for Hispanic families. It is now well documented that early participation in ASD-specialized intervention can lead to significant improvements in skills and behavior for toddlers with ASD. However, despite the availability of publicly funded Part C early intervention (EI) services, long waits for a formal ASD diagnosis can prevent toddlers from receiving appropriately specialized intervention during the critical birth-to-three years. In addition, caregivers concerned about ASD experience high levels of uncertainty and stress during this waiting period. This project will implement and evaluate an innovative healthcare service delivery model designed to promote earlier access to specialized intervention for toddlers with ASD. The Screen-Refer-Treat (SRT) model provides a coordinated and cost-effective approach to early identification and intervention by involving both medical and EI providers, and represents a practical and sustainable strategy for bridging the gap between ASD concerns and ASD intervention. The SRT model, which builds on the availability of validated ASD screening tools and low-cost behaviorally-based ASD interventions, will be implemented in four diverse communities across Washington State to evaluate changes in service delivery practices for toddlers with Hispanic as well as Non- Hispanic backgrounds. The SRT model comprises three components: (1) universal ASD screening at 16-20 months and prompt referral to EI programs by primary care physicians (PCPs); (2) expedited ASD assessments within EI programs; and (3) use of an inexpensive, evidence-based ASD-specialized intervention by EI providers. An electronic version of the Modified Checklist for Autism (M-CHAT) with automated scoring that incorporates relevant follow-up questions will be provided to PCP practices, and distance coaching via telemedicine will be available to EI providers to support their ASD assessment and intervention activities. A stepped wedge cluster RCT design will be used to evaluate implementation and outcomes of the SRT model. Data on screening, referral, assessment, and intervention practices will be collected from 40 PCPs and 80 EI providers across the state prior to and following SRT implementation to identify practice changes. In addition, separate samples of caregivers of toddlers with ASD concerns (n=245) will be recruited from communities before and after SRT implementation and followed prospectively to measure differences and changes over time in caregiver well- being, parenting efficacy, satisfaction with healthcare systems, and toddler's social-communicative behaviors. We predict that implementation of the SRT model will be associated with higher rates of ASD screening by PCPs, earlier referral to EI programs, earlier initiation of ASD-specialized intervention, reduced time between ASD concerns and diagnosis, and improved caregiver and child outcomes.